An over-lit and under-lit environment tires the eyes, and may even cause damages to the eyes. Therefore, the appropriate luminance in an environment to prevent eyes from fatigue is an important issue. A Central Standard Bureau defines regulations on the required illumination for different occasions. For example, the illumination for a classroom is 200-750 Lux, 300-1500 Lux for the blackboard, more than 500 Lux for the desk top, 750-1500 Lux for offices and designing room, and 75-150 Lux for the break room and warehouse.
In addition to the sufficient illumination, the distribution of the illumination is also important, called the uniformity of luminous brightness distribution. The more uniformly distributed the light, the less stress on the eyesight. Therefore, how to provide a comfortable environment with appropriate and balanced lighting of general ambient lighting, such as ceiling light, and local lighting, such as table lamps, is an important issue.
Taiwan Patent No. M284176 disclosed a lighting apparatus integrating illumination sensor and light emitting diode (LED) as a light source. The LED and sensor are wired together. The apparatus uses the sensor to sense the ambient illumination, transmits the detected illumination to the apparatus, and adjusts the current to control the illumination of the LED.
U.S. Pat. No. 6,548,967 disclosed universal lighting network methods and systems. The lighting devices of the lighting network systems are all adjustable and controlled by a control center. The control center uses a wired network to transmit the control signals. The lighting devices may include a plurality of sensors, and monitor the environment. The disclosed patent neither teaches how the control center controls the lighting devices nor how the user's demand can be taken into account in adjusting the lighting.
Proc. Of ACM Int'; Conference on Embedded Networked Sensor Systems, 2005 disclosed a paper entitled “Intelligent light control using sensor networks”. The paper disclosed a lighting control system using a wireless sensing technology. The system takes the user's demands and energy-saving concerns into account. The user may define the lighting preference. In the disclosure, only a lighting control device is considered, and the lighting control method for the device must know in advance of all the relation between lighting calibration level and illumination. The lighting control result may not meet all the user's demands in this case.